Accuracy improvement of built-in torque sensing for harmonic drives

Built-in torque sensing for Harmonic Drives is attractive since it maintain s mechanical characteristics of the gear while providing detection of the t ransmitted torque. Torque sensing by using strain gauges has been studied, but is not widely used yet due to a relatively high signal fluctuation, whi ch is generated by the gear operation. Characteristics of the signal fluctu ation are analyzed in this paper, and a method to effectively compensate th e signal fluctuation is proposed. The signal fluctuation is perfectly compe nsated by adjustment of the strain gauges' sensitivities. A minimum number of strain gauges needed to compensate the signal fluctuation is derived. Th e experimental result with three strain gauges compensating the basic frequ ency component of the signal fluctuation is shown.